"The victim boarded the vessel alone, with the aid of a walker, and sat briefly with a couple of crewmembers and mentioned nothing whatsoever of his intentions," says Casco Bay Lines. Shortly after getting underway, he proceeded out onto the stern of the vessel. Sounds described as resembling firecrackers were heard by crew and some passengers.

"It is believed the shots were fired by a single pistol. It is reported the gentleman was wearing a shoulder holster and the weapon was concealed when he boarded the vessel," says Casco Bay Lines.

Casco Bay Lines says it will be reviewing the incident to determine whether its emergency procedures should be updated.